Mr Coan made that Statement in an interview with Mark Rippetoe and Marty Gallagher.
Thought about that comment for a while my conclusion was his focus is on hitting his cues of the lift rather than getting distracted by the numbers. Not knowing the weight eliminated one aspect of the mental game of heavy weights. He created more of a single minded focus.

Be interested to hear Mr Coan's reasons for this approach.

I really liked Mark Rippetoe's interviews, I remember they spent maybe a quarter of the interview talking about how raw is not what raw used to be.. especially there bit about the monolift.

I think if we watched that interview again we would pick up why he did it. He did more volume than most, did higher rep ranges 5-6, and didn't max out in the gym. In the meets he was ready to max out whatever the weight was. It always seemed to me the end of one meet started the preparation for another like most power lifters... but not missing and not maxing out (often) seem like key points every lifter would be wise to listen to.